Detergent tablet

ABSTRACT

IN A WATER-SOLUBLE COMPRESSED DETERGENT TABLET HAVING AN INTERPARTICULATE AIR FILLED VOID VOLUME BETWEEN 35% AND 60% OF THE TOTAL TABLET VOLUME, THE PROVISION OF ONE OR MORE AIR ESCAPE PASSAGEWAYS EXTENDING FROM THE CORE OF THE TABLET TO AN OUTER SURFACE, THE CROSS-SECTIONAL DIMENSIONS OF THE PASSAGEWAYS RANGING FROM ABOUT .5 MM. TO ABOUT 1.5 MM.

Jan. 19, 1971 R. L. MORRIS ETAL 35 M DETERGENT TABLET Filed June 21, $967 Fig. 5

INVENTORS Robert L. Morris and John R. Castle TORNEY United States Patent 3,557,003 DETERGENT TABLET Robert L. Morris, Cincinnati, and John R. Castle, Springfield Township, Hamilton County, Ohio, assignors to The Procter & Gamble Company, Cincinnati, Ohio, a

corporation of Ohio Filed June 21, 1967, Ser. No. 647,825 Int. Cl. Clld 17/00 U.S. Cl. 252-90 7 Claims ABSTRACT OF THE DISCLOSURE In a water-soluble compressed detergent tablet having an interparticulate air filled void volume between 35% and 60% of the total tablet volume, the provision of one or more air escape passageways extending from the core of the tablet to an outer surface, the cross-sectional dimensions of the passageways ranging from about .5 mm. to about 1.5 mm.

FIELD OF INVENTION This invention relates to water-soluble detergent compositions in a tablet form adapted to promote rapid dissolution. More particularly, it relates to water-soluble detergent tablets which possess good strength and abrasion resistance and are capable of dissolving rapidly even under adverse washing conditions, i.e., in cool Water and after standing in unagitated water prior to their use in an agitated system.

BACKGROUND OF INVENTION Pre-measured amounts of detergent compositions which are compressed into water-soluble tablet form are well known and have received substantial commercial acceptance. They generally comprise a cleaning agent such as a synthetic detergent or soap and a detergency builder which is generally sodium tripolyphosphate (STP), along with suds builders, soil suspending agents and other ingredients commonly added to washing compositions. They are easy to use, avoid the problem of spillage during use, and prevent the use by the consumer of too much or too little detergent. While the use of high pressure tableting can make the tablet strong enough to resist breakage, and while the tablets can be made sufliciently abrasion resistant by treating the surface of the tablet with water or certain coating materials, these processing operations tend to increase the time which is required to dissolve the tablet in water, particularly when cool water must be used. The use of water with temperatures of less than 130 F. is quite common in many parts of the world.

The problem of tablet dissolution rates in particularly acute when the tablet is allowed to stand in unagitated water for a short time prior to beginning the agitation, as when the tablet is pre-soaked, i.e., placed in a washer while the water and laundry are being added. Under these circumstances the time of dissolution after agitation has begunis often greatly increased. Since this results in a loss of a substantial portion of the cleaning power, this delay in dissolving presents a serious problem to the large number of consumers who normally add tablets to unagitated water.

It is believed that one reason for the slower dissolving times in pre-soaked prior art tablets containing STP is as follows. It is the nature of unhydrated STP, when in the presence of a very limited amount of water, to form an unstable super-saturated solution. Beginning shortly thereafter, this supersaturated solution precipitates STP hexahydrate crystals until the normal solubility level of the STP in the water present is reached. When a detergent tablet which contains a relatively high amount of STP is placed in an agitated solution, the surface components of the tablets are rapidly removed by the action of the water. This is both a solubilizing and an eroding action, the latter action removing the particles of the tablet as the binding forces are weakened by the penetration of the water. The particles being thus dispersed, the speed of dissolving is increased. Also, the particle removal process allows the penetration of the water into the tablet to be sufficiently rapid to prevent the above-described supersaturated solutions of STP in water from existing at any point within the tablet for any undue period of time which, in turn, would prevent the formation of the precipitated STP hexahydrate crystals as described above. On the other hand, when the tablet is placed in an unagitated system, the eroding action of the water upon the tablet does not take place. However, the water does gradually penetrate into the tablet, being retarded by the entrapment of air in the tablet core by a viscous neat phase formed by the detergent surfactant, as will be described hereinbelow. Thus, there is created a slowly moving wet-dry interface which surrounds the core of the tablet. The low concentration of water at this relatively stationary interface allows the above-described supersaturation phenomenon to take place and a layer of STP hexahydrate crystals are precipitated out of the supersaturated solution. Under these circumstances, the hexahydrate crystals form bridges between adjacent STP granules, thus creating a shell of interconnected STP granules and STP hexahydrate crystals around a core of the tablet.

In addition to hindering further pentration of water into the tablet, this shell offers substantial resistance to the eroding action of agitated water. Therefore, even if subsequently placed in an agitated system, the movement of the wet-dry interface into the tablet is quite slow and allows a continued formation of supersaturated STP solution and a continued precipitation of the abovedescribed bridge-forming hexahydrate crystals, thus perpetuating the protective shell. It is not uncommon for a tablet with a normal dissolving time of about 60 seconds in an agitated system to have a dissolving time of 500 to 600 seconds when pre-soaked for a short time prior to its addition to the agitated system.

Another reason for slow dissolving time is believed to be that as water enters a tablet, it forms a very viscous, slowly soluble, neat phase with the detergent surfactant, preventing the escape of air from the central portion of the tablet and causing a buildup of air pressure within the tablet. The pressure of the entrapped air retards the rate at which water can enter the core. It will be recognized, therefore, that there is interaction between the two causes of slow dissolving discussed. For example, the hexahydrate formation causes removal of water from the neat phase of the detergent surfactant, making the same more viscous and therefore aggravating the condition. Similarly, the entrapment of air by the neat phase of the detergent surfactant encourages the hexahydrate formation. 1

One method of solving the problem of tablet dissolution is to treat anhydrous granular STP which is to be used in detergent tablets with a fine spray of water to hydrate to the hexahydrate state substantially all of the STP which forms the surface of such granules. When this is done, substantially all of the anhydrous STP granules are encapsulated with STP hexahydrate. When these granules are used to form detergent tablets there is relatively little free, exposed and unhydrated STP available to form a shell of interconnected STP granules and STP hexahydrate crystals. As a result of the eroding action of agitated water upon the tablet after pre-soaking is about the same as if the tablet had been placed directly into a agitated system. However, this method has certain drawbacks since STP is normally purchased in the anhydrous state and since hydration involves an extra step in the preparation of granules used in forming detergent tablets, a step which might not be conveniently performed by some detergent tablet manufacturers. For this rearson, or if for any other reason, a detergent table manufacturer does not wish to hydrate STP, a different technique in solving the problem of slow tablet dissolution is necessitated. In addition, this solution does not improve the situation greatly where the problem is the formation of the neat phase of the detergent surfactant and does not involve the STP hexahydrate formation. Moreover, even if hydration of STP as suggested above is employed, supplementary means to improve the speed of tablet dissolution of the so-hydrated product would also be of interest to table manufacturers and consumers since the ultimate goal in this respect is instantaneous dissolution.

OBJECTS Therefore, it is an object of this invention to provide an improved water-soluble, particulate tablet.

It is another object of this invention to provide a strong and abrasion-resistant detergent tablet which has a rapid speed of dissolution in water.

It is a still further object of this invention to provide adetergent tablet which dissolves rapidly even though allowed to stand in unagitated water prior to its use in an agitated system.

SUMMARY OF INVENTION Briefly stated, in accordance with one aspect of the present invention, there is provided a water-soluble, compressed, particulate tablet having an interparticulate air-filled void volume in the range of from about 35% to about 60% of the total tablet volume. The tablet is provided with at least one air escape passageway extending from the tablet interior to its outer face and having a depth which is from about 25% to about 95% of the corresponding dimension of the tablet. The passageway has a diameter in the range of from about 0.5 mm. to about 1.5 mm.

DESCRIPTION OF DRAWINGS While the specification concludes with claims particu larly pointing out and distinctly claiming the subject matter which is regarded as the present invention, it is believed that the invention will be better understood from the following description and examples taken in connection with the accompanying drawing in which:

FIG. 1 is a plan view, illustrating one preferred embodiment of a water-soluble detergent tablet of the present invention; and

FIG. 2 is a vertical sectional view of the detergent tablet taken along the line 22 of FIG. 1.

Referring to the drawing, there is illustrated a watersoluble detergent tablet which comprises granules of a detergent composition which have been compressed into an integral structure of suificient strength to resist compressive and impact forces experienced in commercial handling and shipment. The apparatus in which such tablets can be formed can be any device which provides a cavity for holding the granules, opposing dies, both of which can be preferably rotated with respect to the tablet faces, and a means for compression of the granular composition, preferably by exerting pressures in the range of from about 150 p.s.i.g. to about 350 p.s.i.g. One very suitable form of apparatus is described in US. letters Patent 3,014,240, issued to Robert V. Burt on Dec. 26, 1961. As is common in this form of product, the structure is porous and includes a network of interconnected intersticial spaces (interparticulate voids) which are occupied by air.

Tablet 10 can be of any commercially feasible size and shape since this does not aifect the present invention in any respect. As shown, tablet 10 has a circular periphery 12 and chamfered upper and lower edges 14 and 16 of frusto-conical shape, a circular top panel 18 and a similarly configured bottom panel 20. This is an easily pressed shape which does not have sharp corners which can be easily broken prior to use. Tablets of this configuration have been used commercially and therefore are familiar to those skilled in the art. The detergent tablet 10 can, for example, weigh between about 1 to about 4 ounces and an average 2 ounce tablet can be dimensioned to have about a 2%" diameter, a thickness (from top panels 18 to bottom panel 20) of about 1", top and bottom panels 18 and 20 having a diameter of approximately 1%" and a periphery 12 of about /2" width.

Extending in the direction of the tablet 10 thickness from the top panel 18 toward bottom panel 20 are a pair of spaced, parallel passageways 22. These can be punched, drilled or otherwise formed in the tablet 10. The purpose of the passageways 22 is to provide an avenue of escape for air trapped Within the interparticulate voids within the tablet 10 when the same is placed in water and the water penetrates into the tablet 10 interior. The passageways 22 must be small enough in section to prevent water from entering them and large enough to prevent them from becoming blocked by fusion or solu tion of granules. In this connection, the smallest transverse dimension must be in the range of from about 0.5 mm. to about 1.5 mm. The cross-section of a passageway 22 is difficult to measure accurately, and so the foregoing dimensions and subsequent discussion of cross-section configuration and sizes are given on the basis of the corresponding dimensions of the instrument, i.e., the punch, drill or the like, used to form the passageway. The passageways 22 can have any desired cross-sectional shape but preferably are round and have diameters in the range of from about 0.75 mm. to about 1.25 mm. Sim ilarly, the passageways 22 must be long enough to extend into the central portion of the tablet 10 but should not extend completely through the product. Broadly, the length of each passageway 22 should be at least about 25% of the corresponding dimension of the tablet 10 and less than about thereof. The preferred limits of such length, however, are from about 35% to about 65% of such corresponding dimension.

Although the number of passageways 22 shown on the drawing is two, the only limitation in this regard is that the same should not be so numerous as to weaken the structure of the tablet 10 to such an extent as to cause damage by normal compressive and impact forces associated with commercial transport and handling. On the other hand, of course, there should be at least one such passageway 22. Preferably, for products of the above description, the number of passageways 22 is in the range of from 1 to about 5.

If it is possible that the tablet will remain stationary in the water, it is desirable to have at least two oppositely disposed passageways to assure that at least one will be in a position to release the entrapped air. Aside from this, the arrangement of the air escape passageways 22, where a plurality of the same is present, is such that, preferably, the centrally located portions of passageway 22 are not separated by a distance greater than about 50% of the maximum dimension of tablet 10 and are not closer than about 15% of such dimension. Thus, the passageways 22 illustrated both extend from top panel 18, but it is feasible to have the same extend from opposite panels, radially or in any direction which is desirable from a manufacturing standpoint. Although the passageways are shown in the drawing as parallel, this relationship is not essential.

The tablet 10 can be made from detergent granules comprising from about 5% to about 50% by weight of a detergent surfactant and from about to about 95% by weight of water-soluble organic or inorganic builder salts, both of which will be more fully discussed hereinafter.

In addition to the abovedescribed ingredients, the detergent tablets 10 of this invention can also contain soap and any of the minor additives commonly used with detergent compositions. Soap, if used, should be present in an amount not over about 10% by weight of the tablet, and preferably, not over about Soaps acceptable for use in this invention are the ordinary alkali metal soaps such as the sodium and potassium salts of the higher fatty acids of naturally occurring plant or animal esters (e.g., palm oil, coconut oil, babassu oil, soybean oil, castor oil, tallow, whale and fish oils, grease and lard, and mixtures thereof) or of synthetically produced fatty acids (e.g., rosin and those resin acids in tall oil) and/ or of naphthenic acids. Sodium and potassium soaps can be made by direct saponification of the fats and oils or by the neutralization of the free fatty acids which are prepared in a separate manufacturing process.

The minor additives mentioned above include: bleaching agents, such as water-soluble perborates or persulfates; suds builders, such as fatty acid amides or ethanolamides wherein the fatty acid radical contains from about 8 to about 20 carbon atoms; suds depressers, such as fatty acids or their soaps; soil suspending agents, such as carboxymethyl cellulose; inorganic salts, such as sodium or potassium sulfates or chlorides; and optical brighteners, dyes, and perfumes. The inorganic salts can be present in an amount of up to about 30% by weight of the tablet, preferably not more than about 20%. The remaining minor ingredients can be present up to a total of about by weight of the tablet.

The detergent materials which can be used in the detergent granules in the tablets of the present invention are those of the anionic, nonionic, long chain tertiary amine oxides, long chain tertiary phosphine oxides, long chain dialkyl sulfoxides, ampholytic or Zwitterionic classes. The detergent materials can be per se in the form of detergent granules, as described above, or blended with other tablet components such as builders, as described below, to form detergent granules.

Examples of detergent materials which can be used in the tablets of this invention include:

(a) Anionic synthetic detergents-This class of synthetic detergents can be broadly described as the watersoluble salts, particularly the alkali metal salts, of organic sulfuric reaction products having in the molecular structure an alkyl radical containing from about 8 to about 22 carbon atoms and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals. Important examples of the synthetic detergents which form a part of the preferred compositions of the present invention are the sodium or potassium alkyl sulfates, especially those obtained by sulfating the higher alcohols produced by reducing the glycerides of tallow or coconut oil; sodium or potassium alkyl benzene sulfonates, in which the alkyl group in a straight or branched chain contains from about 9 to about carbon atoms, and the types described in US. Pat. Nos. 2,220,099 and 2,477,383; sodium alkyl glyceryl ether sulfonates, especially those ethers of the higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulfates and sulfonates; sodium or potassium salts of sulfuric acid esters of the reaction product of one mole of a higher fatty alcohol (e.g., tallow or coconut oil alcohols) and about three moles of ethylene oxide; sodium or potassium salts of alkyl phenol ethylene oxide ether sulfates with an average of about four units of ethylene oxide per molecule and in which the alkyl radicals contain about 9 carbon atoms; the reaction product of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil; sodium or potassium salts of fatty acid amide of a methyl taurine in which the fatty acids, for example, are derived from coconut oil; and others known in the art, a number being specifically set forth in US. Pat. Nos. 2,486,921, 2,486,922 and 2,396,278.

(b) Nonionic synthetic detergents-This class of synthetic detergents can be broadly defined as compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound, which can be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

For example, a well-known class of nonionic synthetic detergents is made available on the market under the trade name of Pluronic. These compounds are formed by condensing ethylene oxide with a hydrophobic base formed by the condensation of propylene oxide with propylene glycol. The hydrophobic portion of the molecule which, of course, exhibits water-insolubility has a molecular weight of from about 1500 to 1800. The addition of polyoxyethylene radicals to this hydrophobic portion tends to increase the water-solubility of the molecule as a whole and the liquid character of the products is retained up to the point where polyoxyethylene content is about 50% of the total weight of the condensation product.

Other suitable nonionic synthetic detergents include:

(i) The polyethylene oxide condensates of alkyl phenols, e.g., the condensation products of alkyl phenols having an alkyl group containing from about 6 to 12 carbon atoms in either a straight chain or branched chain configuration, with ethylene oxide, the said ethylene oxide being present in amounts equal to 10 to 25 moles of ethylene oxide per mole of alkyl phenol. The alkyl substituent in such compounds may be derived from po1ymerized propylene, diisobutylene, octanne, or nonane, for example.

(ii) Those derived from the condensation of ethylene oxide with the product resulting from the reaction of propylene oxide and ethylene diamineproducts which can be varied in composition depending upon the balance between the hydrophobic and hydrophilic elements which is desired. For example, compounds containing from about 40% to about polyoxyethylene by weight and having a molecular weight of from about 5,000 to about 11,000, resulting from the reaction of ethylene oxide groups with a hydrophobic base constituted of the reaction product of ethylene diamine and excess propylene oxide, said base having a molecular weight of the order of 2,500 to 3,000, are satisfactory.

(iii) The condensation products of aliphatic alcohols having from 8 to 18 carbon atoms, in either straight chain or branched chain configuration, with ethylene oxide, e.g., a coconut alcohol ethylene oxide condensate having from 10 to 30 moles of ethylene oxide per mole of coconut alcohol, the coconut alcohol fraction having from 10 to 14 carbon atoms.

(c) Long chain tertiary amine oxides corresponding to the following general formula, R R R N- O, wherein R is an alkyl radical of from about 8 to about 18 carbon atoms, and R and R are each methyl or ethyl radicals. The arrow in the formula is a conventional representation of a semi-polar bond. Examples of amine oxides suitable for use in this invention include dimethyldodecylamine oxide, dimethyloctylamine oxide, dimethyldecylamine oxide, dimethyltetradecylamine oxide, and dimethylhexadecylamine oxide.

(d) Long chain tertiary phosphine oxides corresponding to the following general formula RRR"P- O wherein R is an alkyl, alkenyl or monohydroxyalkyl radical ranging from 10 to 18 carbon atoms in chain length and R and R" are each alkyl or monohydroxyalkyl groups containing from 1 to 3 carbon atoms. The arrow in the formula is a conventional representation of a semi-polar bond. Examples of suitable phosphine oxides are:

dodecyldimethylphosphine oxide, tetradecyldimethylphosphine oxide, tetradecylmethylethylphosphine oxide, cetyldimethylphosphine oxide, stearyldimethylphosphine oxide, cetylethylpropylphosphine oxide, dodecyldiethylphosphine oxide, tetradecyldiethylphosphine oxide, dodecyldipropylphosphine oxide,

dodecyldi (hydroxymethyl) phosphine oxide, dodecyldi (Z-hydroxyethyl) phosphine oxide, tetradecylmethyl-Z-hydroxypropyl phosphine oxide, oleyldimethylphosphine oxide, and Z-hydroxydodecyldimethyl phosphine oxide.

(e) Long chain dialkyl sulfoxides containing one short chain (usually methyl) and one long hydrophobic chain which can contain from about 10 to about 20 carbon atoms. Examples include:

octadecyl methyl sulfoxide, dodecyl methyl sulfoxide, tetradecyl methyl sulfoxide.

(f) Amph-olytic synthetic detergents can be broadly described as derivatives of aliphatic secondary and tertiary amines in which the aliphatic radical can be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to about 18 carbon atoms and one contains an anionic water-solubilizing group, e.g., carboxy, sulfonate, sulfate, phosphate, or phosphonate. Examples of compounds falling with this definition are sodium 3-dodecylaminopropionate, sodium 3-dodecylaminopropane sulfonate, dodecyl-beta-alanine, N-alkyltaurines such as the one prepared by reacting dodecylamine with sodium isothionate according to the teaching of US. Pat. No. 2,658,072, N-higher alkyl aspartic acids such as those produced according to the teaching of US. Pat. No. 2,438,091, and the products sold under the trade name Miranol and described in US. Pat. No. 2,528,378.

(g) Zwitterionic synthetic detergents can be broadly described as derivatives of aliphatic quaternary ammonium, phosphonium, and sulfonium compounds, in which the aliphatic radical may be straight chain or branched, and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an anionic water-solubilizing group, e.g., carboxy, sulfonate, sulfate, phosphate, or phosphonate. A general formula for these compounds is:

wherein R contains an alkyl, alkenyl, or hydroxyalkyl radical of from about 8 to about 18 carbon atoms, from to about 10 ethylene oxide moieties and from 0 to 1 glyceryl moiety; Y is selected from the group consisting of nitrogen, phosphorous, and sulfur atoms; R is an alkyl or monohydroxy alkyl group containing 1 to about 3 carbon atoms; x is 1 when Y is a sulfur atom and 2 when Y is a nitrogen or phosphorous atom, R is an alkylene or hydroxy alkylene of from 1 to about 4 carbon atoms and Z is a radical selected from the group consisting of carboxylate, sulfonate, sulfate, phosphonate, and phosphate groups.

Other examples include:

4- [N,N-di (Z-hydroxyethyl -N-octadecylammonio butane-l-car'boxylate;

5- [S-3 -hydr0xypropyl-S-hexadecylsulfonio -3-hydroxypentanel-sulfate;

3-[P,P-diethyl-P-3,6,9-trioxatetracosanephosphonio1- 2-hydroxypropane-l-phosphate;

3- [N,N-dipropyl-N-3 -dodecoxy-Z-hydroxypropylammonio] -propane-1-phosphonate;

3-( N,N-dimethyl-N-hexadecylammonio) propanel-sulfonate 3- N,N-dimethyl-N-hexadecylammonio -2-hydroxypropanel-sulfonate;

4- N,N-di (2-hydroxyethyl -N- Z-hydroxydodecyl) ammonio -butane-1-carboxylate;

3- [S-ethyl-S- 3-dodecoxy-Z-hydroxypropyl sulfonio] propanel-phosphate;

3- P,P-dimethyl-P'do decylphosphonio] -propanel-phosphonate, and

S- [N,N-di 3-hydroxypropyl -N-hexadecylammonio] 2-hydroxypentanel-sulfate.

Examples of compounds falling within this definition are 3- (N,N-dimethyll-N-hexadecylammonio) -propanel-sulfonate and 3- N,N-dirnethyl-N-hexadecylammonio -2-hydroxypropane- 1-sulfonate which are especially preferred for their excellent cool water detergency characteristics.

The alkyl groups contained in said detergent surfactants can be straight or branched and saturated or unsaturated as desired. The above list of detergent surfactants is exemplary and not limiting. Mixtures of the above detergent surfactants can be used.

Examples of water-soluble inorganic alkaline detergency builder salts are alkali metal carbonates, phosphates, polyphosphates, and silicates, Specific examples of such salts are sodium and potassium tripolyphosphates, carbonates, pyrophosphates, phosphates, and hexametaphosphates. Examples of organic alkaline sequestrant builder salts are:

(1) Amino polycarboxylates, which include alkali metal (sodium, potassium, etc.), ammonium and substituted ammonium (substituted ammonium, as used herein, includes mono-, diand triethanolammoniu-m cations) salts of the following acids: ethylenediaminetetraacetic acid, N-(Z-hydroxyethyl)-ethylenediaminetriacetic acid, N (2 hydroxyethyl)-nitrilodiacetic acid, diethylenetriaminepentaacetic acid, 1,2-diaminocyclohexanetetraacetic acid and nitrilotriacetic acid. The trisodium salts of the above compounds are commonly used.

(2) Alkali metal salts of phytic acid (e.g., sodium and potassium phytatessee US. Pat. 2,739,942;

(3) Polyphosphonates, including specifically sodium and potassium salts of methylene diphosphonic acid, sodium and potassium salts of ethylene diphosphonic acid, sodium and potassium salts of ethane-l-hydroxy-l,1-diphosphonic acid and sodium and potassium salts of carbonyldiphosphonic acid.

Examples of the above polyphosphonic compounds are disclosed in US. Pats. 3,159,581 and 3,213,030 and US. patent applications, Ser, No. 266,055, filed Mar. 18, 1963 and now US. Pat. 3,422,021; Ser. No. 368,419, filed May 18, 1964 and now abandoned; Ser. No. 517,073, filed Dec. 28, 1965 and now US. Pat. 3,422,137; Ser. No. 507,662, filed Nov. 15, 1965 and now US. Pat. 3,400,176; and Ser. No. 489,637, filed Sept. 23, 1965 and now US. Pat. 3,400,148.

(4) Water-soluble salts of polycarboxylic polymers and copolymers, as described in US. Pat. 3,308,067, i.e., a polyelectrolyte builder material consisting of water-soluble salts of a polymeric aliphatic polycarboxylic acid selected from the group consisting of (a) water-soluble salt of a homopolymer of an aliphatic polycarboxylic acid having the following empirical formula:

wherein X, Y and Z are each selected from the group consisting of hydrogen, methyl, carboxyl, and carboxymethyl, at least one of X, Y, and Z being selected from the group consisting of carboxyl and carboxymethyl,

provided that X and Y can be carboxymethyl only when Z is selected from carboxyl and carboxymethyl, wherein only one of X, Y and Z can be methyl, and wherein n is a whole integer having a value within a range, the lower limit of which is three and the upper limit of which is determined by the solubility characteristics in an aqueous system;

(b) a water-soluble salt of a copolymer of at least two of the monomeric species having the empirical formula described in (a); and

(c) a water-soluble salt of a copolymer of a member selected from the group of al'kylenes and monocarboxylic acids with the aliphatic polycarboxylic compounds described in (a), said copolymers having the general formula:

it it ill R (l-m) Y C m n wherein R is selected from the group consisting of hydrogen, methyl, carboxyl, carboxymethyl, and carboxyethyl; wherein only one R can be methyl; wherein m is at least 45 mole percent of the copolymer; wherein X, Y and Z are each selected from the group consisting of hydrogen, methyl, carboxyl, and carboxymethyl; at least one of X, Y and Z being selected from the group of carboxyl and carboxymethyl provided that X and Y can can be carboxymethyl only when Z is selected from the group of carboxyl and carboxymethyl, wherein only one of X, Y and Z can be methyl; and wherein n is a whole integer within a range, the lower limit of which is three and the upper limit of which is determined primarily by the solubility characteristics in an aqueous system; said polyelectrolyte builder material having a minimum molecular weight of 350 calculated as the acid form and an equivalent 'weight of about 50 to about 80, calculated as the acid form, (e.g., polymers of itaconic acid, aconitic acid; maleic acid; mesaconic acid; fumaric acid; methylene malonic acid; and citraconic acid and copolymers with themselves and other compatible monomers such as ethylene); and Mixtures thereof.

Mixtures of any and all of the organic and/or inorganic builders can be used.

It is necessary for successful operation of the present invention that the finished tablet have sufiicient interparticle channeling to allow the Water to penetrate into the tablet. This penetration serves to loosen the materials near the surface of the tablet, thus enabling the action of the water in an agitated system to more easily disperse and dissolve them. This penetration is also necessary to prevent a troublesome wet-dry interface within the tablet as described above. Therefore, the granules of synthetic detergent and builder which comprise the detergent tablet should be of suflicient size to provide an interparticulate void volume of about 35 to about 60% of the total tablet volume. Such granules should not be so large, however, as to make it difficult to obtain uniformity in the composition of the tablets, or diflicult to process them. Therefore, the detergent and builder granules for use in this invention should be of such a size that substantially all will pass through a standard 6 mesh screen (Tyler) and that at least about 95% will stay on a standard 100 mesh screen y r)- Similarly, any optional ingredients for use in this tablet, should preferably be of a size comparable to the builder and detergent granules. If substantially different, they should not be used in such an amount as would prevent uniformity of product, or would either interfere with tablet processing or with the formation of the interparticulate channels of the tablet.

The following examples are given to illustrate the manner in which this invention can be practiced.

EXAMPLE I A spray-dried granular detergent composition having the following composition is formed:

Parts by weight Sodium tripolyphosphate 28 Sodium alkyl benzene sulfonate (the alkyl radical being derived from polypropylene and averaging 12 carbon atoms) 20 Sodium sulfate 27 Sodium silicate having an SiO to Na O ratio of 2:1 14 Sodium carboxymethyl cellulose 0.7 Optical brightener: 0.14 A 1:1 mixture of Pluronic F68 and D64 (condensation products of ethylene oxide and propylene glycol having molecular weights of about 8000 and 3000 respectively) 1 2.8 A mixture of hydrogenated fish oil fatty acids (a suds depresser described in British Pat. 808,945) 2.8

Moisture 4 The Pluronic mixture is added to chemically deaerate the crutcher mix which is spray-dried in order to obtain high density granules. See British Pat. 812,29.

The spray-dried composition has a density of 0.5. Then an additional 0.92% (by weight of the spray-dried granular composition) of Pluronic L64 is sprayed uniformly on the granules in a rotary drum. This nonionic detergent spray-on is used to act as a binding agent during tablet compression. The granules are then subjected to an air lift, a gravity separator and a screen whereby the moisture content is reduced to 3% and particles larger in size than 1.4 mm. and most of the particles smaller in size than .2 mm. (mean diameter) are removed. The resulting spraydried composition contains 18% particles having a size smaller than .2 mm.

990 parts of this spray-dried composition are uniformly mixed with 840 parts of anhydrous granular sodium tripolyphosphate which contains 2% particles smaller in size than .2 mm. The density of the sodium tripolyphosphate is 1.3. The resulting mixture contains 1.7% moisture substantially all of which was in the spray-dried granules. The mixture contains 10.6% particles smaller in size than .2 mm. The average particle density of the mixture is 0.85. 2 parts by weight of perfume is sprayed on the mixture.

Then a number of tablets are made as follows: 6.2 cubic inches of the mixture is charged into a tablet cavity having a diameter of 2% inches. One tablet die is forced onto the mixture with a pressure of 200 psi. to form the mixture into a tablet having a volume of 3.2 cubic inches. Both the compression die and the non-yielding die opposing this die are rotated with respect to the tablet. The non-yielding die is rotated through an arc of 10 during the period of maximum compression. The compression die is rotated in a direction opposite to that of the nonyielding die through an arc of 10 during the first part of the period of maximum compression and in the same direction as that of the compression die through an arc of 10 during the last part of the period of maximum compression. The rotating dies exert a definite shearing force on the faces of the tablet being formed.

There is no tendency for the tablet or the tablet ingredients to adhere to the dies which, when drawn apart permit the tablet to be easily removed. Each tablet is then placed on a three-pronged support and passed through a chamber where the entire surface of the tablet is subjected to a fine spray of water. During this treatment 2 /2% water (by weight of the tablet) is added to the tablet surface. The tablet is then placed in a drying oven at 250 F. for 1.5 minutes. Sodium tripolyphosphate on the surface of the tablet hydrates and detergent ingredicuts on the surface of the tablet cement together, forming a non-chalkly, abrasion-resistant porous surface on the tablet. When the tablet is removed from the oven it is only slightly clamp to the touch and is ready for packaging. It weights two ounces, is sized as indicated previously for a two ounce product, and has a total moisture content of 3.3%. It has a network of voids amounting to 45% of the volume of the tablet. This network is predominantly interparticulate.

A number of tablets made as described above are tested for speed of dissolving by punching round air escape passageways of varying size and number in the tablet top panels. The tablets are then tested for average speed of disintegration in a cylindrical chamber having a closed bottom and water inlet ports on the side and bottom whereby to develop a rotating column of water to cause the tablets to spin, tumble, impact and be abraded. The following tabulates the results:

Tablet Number of Passageway test air escape Diameter of depth as letter passageways air escape percent of 4 identiformed in passageways tablet Dissolvmg fication tablet in m.m. thickness time 1 None 100 1 1. 1 50 70. 8 2 1. 1 50 58. 4 3 l. 1 50 59. 7 4 1. 1 50 55. 6 4 l. 1 100 86. 2 4 56 50 69. 4 1 1. 63 50 94. 5

1 As percent of time of dissolution of tablet without air escape passage ways.

This example illustrates that maximum benefits are derived, in the tablets under test, using four air-escape passageways having a diameter of 1.1 mm. and a depth of 50% of the tablet thickness, test E. When the diameter of the passageway is made greater than 1.5 mm. (test H) or the passageway extends completely through the tablet (test F), the dissolving time approaches that of tablets which do not have air-escape passageways thereon (test A).

Other tablets are prepared having from 1 to 4 airescape passageways with diameters of 0.75 mm., 1.25 mm. and 1.50 mm. and having depths of 25%, 35%, 65% and 95% of the corresponding dimension of the tablets and similarly satisfactory results are achieved, whether (in the case of a plurality of passageways) the passageways extend to one or different surfaces of the tablet. Those having diameters in the range of 0.75 mm. to 1.25 mm. and lengths of from 35% to 65% of the corresponding dimension of the tablet are particularly outstanding. Speed of dissolving is only marginally improved with the addition of further passageways and when five passageways are employed a reduction of the strength of a the tablet starts to occur so that the employment of more than five passageways becomes undesirable from the standpoint of potential tablet breakage in subsequent handling and shipment.

EXAMPLE II The following ingredients are mechanically uniformly mixed:

Parts by weight Anhydrous granular sodium tripolyphosphate containing 2% particles smaller in size than .2 mm.

The average particle density of the mixture is 1.3.

6 cubic inches of this mixture is placed in a tablet cavity having a diameter of 2%". One tablet die is forced onto the mixture with a pressure of 180 p.s.i. to form the mixture into a tablet having a volume of 3.2 cubic inches. Both the compression die and the non-yielding die opposing this die are rotated with respect to the tablet during the period of maximum compression. Both dies are rotated through an arc of 10 around the axis of compression and in opposite directions. The rotating dies exert a definite shearing force on the faces of the tablet being formed.

There is no tendency for the tablet or the tablet ingredients to adhere to the dies which, when drawn apart, permit the tablet to be easily removed. The entire surface of the tablet is then sprayed with water in an amount equivalent to 2 /2 by weight of the tablet. The tablet is permitted to air dry at room temperature. Sodium tripolyphosphate on the surface of the tablet hydrates and detergent ingredients on the surface of the tablet cement together, forming a non-chalky, abrasion-resistant porous surface on the tablet.

The tablet weighs 2 ounces, is sized as previously indicated and has a total moisture content of 3%. It has a network of voids amounting to of the volume of the tablet. This network is predominantly interparticulate.

A number of tablets made as described in this example are tested for speed of dissolving. Four 1.1 mm. diameter air escape passageways each /2" long, are formed in one panel of some of the tablets. In these tablets one passage- Way is aligned axially and the other three equally spaced along a circular path concentric with the axis of the tablet and having a radius equal to about half the radius of the major tablet diameter. The dissolving time of the tablets with the air escape passageways therein is at least about 30% less than the dissolving time of other tablets which do not have such passageways when tested by the apparatus of Example I. The same improvement is dissolving time is found when the tablets being compared (both those with the air escape passageway and those without such passageways) are preesoaked for 1 minute and then tested in such apparatus.

When in the above examples the following water-soluble builder salts are substituted on a weight basis, either wholly or in part (e.g., a 1:1 mixture by weight), for the sodium tripolyphosphate of the detergent compositions 0f the tablets, substantially equivalent results are achieved in that the use of air escape passageways in the sizes,

lengths and arrangements set forth causes a significant reduction of dissolving time of the tablets: potassium tripolyphosphates; sodium silicate; sodium and potassium carbonates, pyrophosphates, phosphates, and hexametaphosphates; aminopolycarboxylates; phytates; polyphosphonates; water-soluble salts of polycarboxylic polymers and copolymers.

The same good results are achieved when in the above examples the following detergent surfactants are substituted on a like basis for the sodium alkyl benzene sulfonate of the detergent compositions of the tablets: tallow and coconut oil alkyl sulfates; potassium alkyl benzene sulfonate; sodium alkyl glyceryl ether sulfonates; sodiumcoconut oil fatty acid monoglyceride sulfates and sulfonates; 'Pluronics, polyethylene oxide condensates of alkyl phenols; condensates of ethylene oxide and the product of the reaction of propylene oxide and ethylene diamine; condensation products of aliphatic alcohols having from 8 to 18 carbon atoms, with ethylene; long chain tertiary amine oxides; long chain tertiary phosphine oxides; long chain dialkyl sulfoxides containing one short chain and one long hydrophobic chain containing from about 10 to about 20 carbon atoms; ampholytic and zwitterionic synthetic detergents.

Similarly good results are achieved when in the above examples the following are substituted in part on a weight basis for the sodium tripolyphosphate and/ or the sodium alkyl benzene sulfonate of the detergent compositions of the tablets: 3% by weight of soap; 10% by weight of bleaching agent; 0.4% by weight of dye; and 0.5% by weight of perfume.

What is claimed is:

1. A water-soluble, compressed, particulate synthetic detergent tablet having an interparticulate air-filled void volume in the range of from about 35% to about 60% of the total tablet volume, said tablet containing from at least one air escape passageway extending from the tablet interior to the outer surface of said tablet, said passageway having a depth which is from about 25% to about 95% of the corresponding dimension of the tablet and cross-sectional dimensions in the range of fromabout 0.5 mm. to about 1.5 mm.

2. The tablet of claim 1 in which the number of said air escape passageways is from 1 to about 5.

3. The tablet of claim 2 in which each air escape passageway has cross-sectional dimensions in the range of from about 0.75 mm. to about 1.25 mm.

4. The tablet of claim 3 in which each air escape passageway has a length which is about 35% to about 65% of said corresponding dimension of said tablet.

5. The tablet of claim 4 in which a plurality of air escape passageways is employed and in which the centrally located portions of said air escape passageways are separated by a distance not in excess of about 50% of the maximum dimension of the tablet and not less than about 15% of the said maximumdimension.

6. A water-soluble, compressed, particulate synthetic detergent tablet formed from particulate matter and containing an air-filled inter-particulate void volume in the range of from about 35% to about 60% of the total tablet volume, the tablet having a composition consisting essentially of:

(A) from to about 95 by weight of water-soluble builder salt selectetd from the group consisting of alkali metal carbonates, alkali metal phosphates, alkali metal polyphosphates, alkali metal silicates, amino polycarboxylates, alkali metal salts of phytic acid, polyphosphonates, water-soluble salts of polycarboxylic polymers and copolymers and mixtures thereof;

(B) from about 5% to about 50% by weight of synthetic detergent surfactant selected from the group consisting of anionics, nonionics, long chain tertiary amine oxides, long chain tertiary phosphine oxides, long chain dialkyl sulfoxides, ampholytic and zwitterionic synthetic detergents, and mixtures thereof;

(C) from 0% to about by weight of alkali metal soaps;

(D) from 0% to about 20% by weight of an inertinorganic salt selected from the group consisting of sodium and potassium sulfates and chlorides;

(E) from 0% to about 10% by weight of minor additives selected from the group consisting of bleaching agents, suds builders, suds depressors, soil suspending agents, optical brighteners, dyes, perfumes, and mixtures thereof; and

(F) the balance, moisture;

said tablet containing from 1 to about 5 air escape passageways extending from the outer surface of said tablet to the interior thereof, said passageways having 'a depth of from about 35% to 65% of the corresponding'fdimensions of the tablet and cross-sectional dimensions in the range of from about 0.75 mm. to about 1.25 mmj'l 7. A water-soluble, compressed, particulate, synthetic detergent tablet containing an air-filled interpar ticulate void volume in the range of from about 35% to about of the total tablet volume and in which the detergent composition contains sodium tripolyphosphate as a detergency builder, said tablet containing from 1 to about 5 air escape passageways extending from the outef. surface of said tablet to the interior thereof, said passageways having a depth of from about 35% to of the corresponding dimension of the tablet and cross-sectional dimensions in the range of from about 0.75 mm. to about 1.25 mm.

References Cited UNITED STATES PATENTS 235,730 12/1880 'Borie. 711,403 10/1902 Klein et al. 1,828,361 10/ 1928 Crary et al. 2,210,924 '8/1940 Hood 252-134 2,339,773 l/l944 Egan. 3,146,169 8/ 1964 Stephenson et al. 3,383,320 5/1968 Bell, '11. 25292 FOREIGN PATENTS 683 1904 Great Britain 252-92 LEO-N D. ROSDOL, Primary Examiner W. SCHULZ, Assistant Examiner US. Cl. X.R.

252134, 174; D=7l1.l 

